PHOTO: Britney Spears flaunts fit bikini bod

The 32-year-old, who kicked off a two-year residency at Las Vegas's Planet Hollywood in December, was looking fit and fabulous in bikini pics she posted to Twitter on Thursday. Spears showed off her toned physique as she vacationed with her boyfriend of just less than a year, David Lucado, and her sons, 8-year-old Sean Preston and Jayden James, 7.

Spears kicked up her workouts in preparation for the "Piece of Me" show, just as she's always done before her tours. However, the work was more difficult this time around. "My body yesterday — I just felt so bad," she revealed to In Style in January. "I had to get two massages in one day! When I was younger I wasn't as likely to rehearse as hard as I do now. I'm harder on myself these days. Before, I would practice two times, and I'd be done. Nowadays, I'm very critical of myself."

Even Brit has to agree that she looks amazing now! Spears is set to return to Sin City on April 25.